1. Field of the Invention
The present invention relates generally to angiographic and other diagnostic or therapeutic catheters and more particularly to a feature of such catheters which prevents high velocity jetting of contrast media, fluid or the like from the distal end opening of such catheters.
2. Discussion of the Prior Art
In diagnostic catheters designed for left ventricular injection of contrast media or dyes or for higher pressure injections into coronary arteries during angiographic and therapeutic procedures, the outside diameter of such catheters is necessarily small, typically in the range of from 3 to 10 Fr. When it is considered that radiographic contrast media is commonly injected at a rapid rate by means of either a power injector or by hand, the liquid contrast media exits the distal end opening of the catheter as a high velocity jet. This may cause "whipping" of the catheter tip and resulting damage to delicate endothelial tissues lining the blood vessels being examined. The velocity and impact of the jet itself may be sufficiently high to damage the vessel wall. Experience has shown that such tissue damage may form the nidus of stenotic lesions and dissections and ultimately to occlusion of such blood vessels.
As is pointed out in the introductory portion of the Cragg Patent U.S. Pat. No. 5,085,635, to minimize undesirable effects of the high velocity jet, prior art catheter designs had sealed distal ends with a plurality of side holes near the distal end to allow the contrast media to exit in a radial direction through several ports, thereby reducing somewhat the overall velocity of the exiting contrast liquid. Even here, it was often too high. Having a closed distal end effectively precluded such catheters from being fed over a guidewire. This, of course, makes it difficult and sometimes unsafe to appropriately place the distal end of the catheter prior to contrast ejection. To address this problem, the angiographic catheter particularly described in the Cragg '635 patent incorporates a normally completed closed leaflet valve arrangement over the end hole of the catheter which permits passage of a guidewire therethrough, but which effectively blocks the flow of contrast media therethrough. Thus, the contrast media exits a plurality of apertures formed through the wall of the catheter tubing proximate the distal end thereof.